There are people who are such meshuggenehs that anybody they tell their crazy ideas to will end up being driven just as crazy.
In a short while the craziness spreads through the population like a plague. When that happens, we're meshugged.

Origin is "meshugge", the Yiddish term for crazy and senseless. Meshuggenehs are people who are meshugge.

Only US citizens can be candidates for President. But there are still people who believe that Obama's not a US citizen! Shit. We're meshugged.